Provided by: openmpi-bin_1.6.5-8_amd64 
NAME
orterun, mpirun, mpiexec - Execute serial and parallel jobs in Open MPI.
Note: mpirun, mpiexec, and orterun are all synonyms for each other. Using any of the
names will produce the same behavior.
SYNOPSIS
Single Process Multiple Data (SPMD) Model:
mpirun [ options ] <program> [ <args> ]
Multiple Instruction Multiple Data (MIMD) Model:
mpirun [ global_options ]
[ local_options1 ] <program1> [ <args1> ] :
[ local_options2 ] <program2> [ <args2> ] :
... :
[ local_optionsN ] <programN> [ <argsN> ]
Note that in both models, invoking mpirun via an absolute path name is equivalent to
specifying the --prefix option with a <dir> value equivalent to the directory where mpirun
resides, minus its last subdirectory. For example:
% /usr/local/bin/mpirun ...
is equivalent to
% mpirun --prefix /usr/local
QUICK SUMMARY
If you are simply looking for how to run an MPI application, you probably want to use a
command line of the following form:
% mpirun [ -np X ] [ --hostfile <filename> ] <program>
This will run X copies of <program> in your current run-time environment (if running under
a supported resource manager, Open MPI's mpirun will usually automatically use the
corresponding resource manager process starter, as opposed to, for example, rsh or ssh,
which require the use of a hostfile, or will default to running all X copies on the
localhost), scheduling (by default) in a round-robin fashion by CPU slot. See the rest of
this page for more details.
OPTIONS
mpirun will send the name of the directory where it was invoked on the local node to each
of the remote nodes, and attempt to change to that directory. See the "Current Working
Directory" section below for further details.
<program> The program executable. This is identified as the first non-recognized argument
to mpirun.
<args> Pass these run-time arguments to every new process. These must always be the
last arguments to mpirun. If an app context file is used, <args> will be
ignored.
-h, --help
Display help for this command
-q, --quiet
Suppress informative messages from orterun during application execution.
-v, --verbose
Be verbose
-V, --version
Print version number. If no other arguments are given, this will also cause
orterun to exit.
To specify which hosts (nodes) of the cluster to run on:
-H, -host, --host <host1,host2,...,hostN>
List of hosts on which to invoke processes.
-hostfile, --hostfile <hostfile>
Provide a hostfile to use.
-machinefile, --machinefile <machinefile>
Synonym for -hostfile.
To specify the number of processes to launch:
-c, -n, --n, -np <#>
Run this many copies of the program on the given nodes. This option indicates that
the specified file is an executable program and not an application context. If no
value is provided for the number of copies to execute (i.e., neither the "-np" nor
its synonyms are provided on the command line), Open MPI will automatically execute
a copy of the program on each process slot (see below for description of a "process
slot"). This feature, however, can only be used in the SPMD model and will return
an error (without beginning execution of the application) otherwise.
-npersocket, --npersocket <#persocket>
On each node, launch this many processes times the number of processor sockets on
the node. The -npersocket option also turns on the -bind-to-socket option.
-npernode, --npernode <#pernode>
On each node, launch this many processes.
-pernode, --pernode
On each node, launch one process -- equivalent to -npernode 1.
To map processes to nodes:
-loadbalance, --loadbalance
Uniform distribution of ranks across all nodes. See more detailed description
below.
-nolocal, --nolocal
Do not run any copies of the launched application on the same node as orterun is
running. This option will override listing the localhost with --host or any other
host-specifying mechanism.
-nooversubscribe, --nooversubscribe
Do not oversubscribe any nodes; error (without starting any processes) if the
requested number of processes would cause oversubscription. This option implicitly
sets "max_slots" equal to the "slots" value for each node.
-bynode, --bynode
Launch processes one per node, cycling by node in a round-robin fashion. This
spreads processes evenly among nodes and assigns ranks in a round-robin, "by node"
manner.
For process binding:
-bycore, --bycore
Associate processes with successive cores if used with one of the -bind-to-*
options.
-bysocket, --bysocket
Associate processes with successive processor sockets if used with one of the
-bind-to-* options.
-cpus-per-proc, --cpus-per-proc <#perproc>
Use the number of cores per process if used with one of the -bind-to-* options.
-cpus-per-rank, --cpus-per-rank <#perrank>
Alias for -cpus-per-proc.
-bind-to-core, --bind-to-core
Bind processes to cores.
-bind-to-socket, --bind-to-socket
Bind processes to processor sockets.
-bind-to-none, --bind-to-none
Do not bind processes. (Default.)
-report-bindings, --report-bindings
Report any bindings for launched processes.
-slot-list, --slot-list <slots>
List of processor IDs to be used for binding MPI processes. The specified bindings
will be applied to all MPI processes. See explanation below for syntax.
For rankfiles:
-rf, --rankfile <rankfile>
Provide a rankfile file.
To manage standard I/O:
-output-filename, --output-filename <filename>
Redirect the stdout, stderr, and stddiag of all ranks to a rank-unique version of
the specified filename. Any directories in the filename will automatically be
created. Each output file will consist of filename.rank, where the rank will be
left-filled with zero's for correct ordering in listings.
-stdin, --stdin <rank>
The MPI rank that is to receive stdin. The default is to forward stdin to rank=0,
but this option can be used to forward stdin to any rank. It is also acceptable to
specify none, indicating that no ranks are to receive stdin.
-tag-output, --tag-output
Tag each line of output to stdout, stderr, and stddiag with [jobid, rank]<stdxxx>
indicating the process jobid and rank that generated the output, and the channel
which generated it.
-timestamp-output, --timestamp-output
Timestamp each line of output to stdout, stderr, and stddiag.
-xml, --xml
Provide all output to stdout, stderr, and stddiag in an xml format.
-xterm, --xterm <ranks>
Display the specified ranks in separate xterm windows. The ranks are specified as a
comma-separated list of ranges, with a -1 indicating all. A separate window will be
created for each specified rank. Note: xterm will normally terminate the window
upon termination of the process running within it. However, by adding a "!" to the
end of the list of specified ranks, the proper options will be provided to ensure
that xterm keeps the window open after the process terminates, thus allowing you to
see the process' output. Each xterm window will subsequently need to be manually
closed. Note: In some environments, xterm may require that the executable be in
the user's path, or be specified in absolute or relative terms. Thus, it may be
necessary to specify a local executable as "./foo" instead of just "foo". If xterm
fails to find the executable, mpirun will hang, but still respond correctly to a
ctrl-c. If this happens, please check that the executable is being specified
correctly and try again.
To manage files and runtime environment:
-path, --path <path>
<path> that will be used when attempting to locate the requested executables. This
is used prior to using the local PATH setting.
--prefix <dir>
Prefix directory that will be used to set the PATH and LD_LIBRARY_PATH on the
remote node before invoking Open MPI or the target process. See the "Remote
Execution" section, below.
--preload-binary
Copy the specified executable(s) to remote machines prior to starting remote
processes. The executables will be copied to the Open MPI session directory and
will be deleted upon completion of the job.
--preload-files <files>
Preload the comma separated list of files to the current working directory of the
remote machines where processes will be launched prior to starting those processes.
--preload-files-dest-dir <path>
The destination directory to be used for preload-files, if other than the current
working directory. By default, the absolute and relative paths provided by
--preload-files are used.
--tmpdir <dir>
Set the root for the session directory tree for mpirun only.
-wd <dir>
Synonym for -wdir.
-wdir <dir>
Change to the directory <dir> before the user's program executes. See the "Current
Working Directory" section for notes on relative paths. Note: If the -wdir option
appears both on the command line and in an application context, the context will
take precedence over the command line. Thus, if the path to the desired wdir is
different on the backend nodes, then it must be specified as an absolute path that
is correct for the backend node.
-x <env>
Export the specified environment variables to the remote nodes before executing the
program. Only one environment variable can be specified per -x option. Existing
environment variables can be specified or new variable names specified with
corresponding values. For example:
% mpirun -x DISPLAY -x OFILE=/tmp/out ...
The parser for the -x option is not very sophisticated; it does not even understand
quoted values. Users are advised to set variables in the environment, and then use
-x to export (not define) them.
Setting MCA parameters:
-gmca, --gmca <key> <value>
Pass global MCA parameters that are applicable to all contexts. <key> is the
parameter name; <value> is the parameter value.
-mca, --mca <key> <value>
Send arguments to various MCA modules. See the "MCA" section, below.
For debugging:
-debug, --debug
Invoke the user-level debugger indicated by the orte_base_user_debugger MCA
parameter.
-debugger, --debugger
Sequence of debuggers to search for when --debug is used (i.e. a synonym for
orte_base_user_debugger MCA parameter).
-tv, --tv
Launch processes under the TotalView debugger. Deprecated backwards compatibility
flag. Synonym for --debug.
There are also other options:
-aborted, --aborted <#>
Set the maximum number of aborted processes to display.
--app <appfile>
Provide an appfile, ignoring all other command line options.
-cf, --cartofile <cartofile>
Provide a cartography file.
--hetero
Indicates that multiple app_contexts are being provided that are a mix of 32/64-bit
binaries.
-leave-session-attached, --leave-session-attached
Do not detach OmpiRTE daemons used by this application. This allows error messages
from the daemons as well as the underlying environment (e.g., when failing to
launch a daemon) to be output.
-ompi-server, --ompi-server <uri or file>
Specify the URI of the Open MPI server (or the mpirun to be used as the server) ,
the name of the file (specified as file:filename) that contains that info, or the
PID (specified as pid:#) of the mpirun to be used as
the server. The Open MPI server is used to support multi-application data
exchange via the MPI-2 MPI_Publish_name and MPI_Lookup_name functions.
-report-pid, --report-pid <channel>
Print out mpirun's PID during startup. The channel must be either a '-' to indi
cate that the pid is to be output to stdout, a '+' to indicate that the pid is to
be outp ut to stderr, or a filename to which the pid is to be written.
-report-uri, --report-uri <channel>
Print out mpirun's URI during startup. The channel must be either a '-' to indi
cate that the URI is to be output to stdout, a '+' to indicate that the URI is to
be outp ut to stderr, or a filename to which the URI is to be written.
-wait-for-server, --wait-for-server
Pause mpirun before launching the job until ompi-server is detected. This is useful
in scripts where ompi-server may be started in the background, followed immediately
by an mpirun command that wishes to connect to it. Mpirun will pause until either
the specified ompi-server is contacted or the server-wait-time is exceeded.
-server-wait-time, --server-wait-time <secs>
The max amount of time (in seconds) mpirun should wait for the ompi-server to
start. The default is 10 seconds.
The following options are useful for developers; they are not generally useful to most
ORTE and/or MPI users:
-d, --debug-devel
Enable debugging of the OmpiRTE (the run-time layer in Open MPI). This is not
generally useful for most users.
--debug-daemons
Enable debugging of any OmpiRTE daemons used by this application.
--debug-daemons-file
Enable debugging of any OmpiRTE daemons used by this application, storing output in
files.
-launch-agent, --launch-agent
Name of the executable that is to be used to start processes on the remote nodes.
The default is "orted". This option can be used to test new daemon concepts, or to
pass options back to the daemons without having mpirun itself see them. For
example, specifying a launch agent of orted -mca odls_base_verbose 5 allows the
developer to ask the orted for debugging output without clutter from mpirun itself.
--noprefix
Disable the automatic --prefix behavior
There may be other options listed with mpirun --help.
DESCRIPTION
One invocation of mpirun starts an MPI application running under Open MPI. If the
application is single process multiple data (SPMD), the application can be specified on
the mpirun command line.
If the application is multiple instruction multiple data (MIMD), comprising of multiple
programs, the set of programs and argument can be specified in one of two ways: Extended
Command Line Arguments, and Application Context.
An application context describes the MIMD program set including all arguments in a
separate file. This file essentially contains multiple mpirun command lines, less the
command name itself. The ability to specify different options for different
instantiations of a program is another reason to use an application context.
Extended command line arguments allow for the description of the application layout on the
command line using colons (:) to separate the specification of programs and arguments.
Some options are globally set across all specified programs (e.g. --hostfile), while
others are specific to a single program (e.g. -np).
Specifying Host Nodes
Host nodes can be identified on the mpirun command line with the -host option or in a
hostfile.
For example,
mpirun -H aa,aa,bb ./a.out
launches two processes on node aa and one on bb.
Or, consider the hostfile
% cat myhostfile
aa slots=2
bb slots=2
cc slots=2
Here, we list both the host names (aa, bb, and cc) but also how many "slots" there are for
each. Slots indicate how many processes can potentially execute on a node. For best
performance, the number of slots may be chosen to be the number of cores on the node or
the number of processor sockets. If the hostfile does not provide slots information, a
default of 1 is assumed. When running under resource managers (e.g., SLURM, Torque,
etc.), Open MPI will obtain both the hostnames and the number of slots directly from the
resource manger.
mpirun -hostfile myhostfile ./a.out
will launch two processes on each of the three nodes.
mpirun -hostfile myhostfile -host aa ./a.out
will launch two processes, both on node aa.
mpirun -hostfile myhostfile -host dd ./a.out
will find no hosts to run on and abort with an error. That is, the specified host dd
is not in the specified hostfile.
Specifying Number of Processes
As we have just seen, the number of processes to run can be set using the hostfile. Other
mechanisms exist.
The number of processes launched can be specified as a multiple of the number of nodes or
processor sockets available. For example,
mpirun -H aa,bb -npersocket 2 ./a.out
launches processes 0-3 on node aa and process 4-7 on node bb, where aa and bb are both
dual-socket nodes. The -npersocket option also turns on the -bind-to-socket option,
which is discussed in a later section.
mpirun -H aa,bb -npernode 2 ./a.out
launches processes 0-1 on node aa and processes 2-3 on node bb.
mpirun -H aa,bb -npernode 1 ./a.out
launches one process per host node.
mpirun -H aa,bb -pernode ./a.out
is the same as -npernode 1.
Another alternative is to specify the number of processes with the -np option. Consider
now the hostfile
% cat myhostfile
aa slots=4
bb slots=4
cc slots=4
Now,
mpirun -hostfile myhostfile -np 6 ./a.out
will launch ranks 0-3 on node aa and ranks 4-5 on node bb. The remaining slots in the
hostfile will not be used since the -np option indicated that only 6 processes should
be launched.
Mapping Processes to Nodes
The examples above illustrate the default mapping of process ranks to nodes. This mapping
can also be controlled with various mpirun options. Here, we consider the same hostfile
as above with -np 6 again:
node aa node bb node cc
mpirun 0 1 2 3 4 5
mpirun -loadbalance 0 1 2 3 4 5
mpirun -bynode 0 3 1 4 2 5
mpirun -nolocal 0 1 2 3 4 5
The -loadbalance option tries to spread processes out fairly among the nodes.
The -bynode option does likewise but numbers the processes in "by node" in a round-robin
fashion.
The -nolocal option prevents any processes from being mapped onto the local host (in this
case node aa). While mpirun typically consumes few system resources, -nolocal can be
helpful for launching very large jobs where mpirun may actually need to use noticeable
amounts of memory and/or processing time.
Just as -np can specify fewer processes than there are slots, it can also oversubscribe
the slots. For example, with the same hostfile:
mpirun -hostfile myhostfile -np 14 ./a.out
will launch processes 0-3 on node aa, 4-7 on bb, and 8-11 on cc. It will then add the
remaining two processes to whichever nodes it chooses.
One can also specify limits to oversubscription. For example, with the same hostfile:
mpirun -hostfile myhostfile -np 14 -nooversubscribe ./a.out
will produce an error since -nooversubscribe prevents oversubscription.
Limits to oversubscription can also be specified in the hostfile itself:
% cat myhostfile
aa slots=4 max_slots=4
bb max_slots=4
cc slots=4
The max_slots field specifies such a limit. When it does, the slots value defaults to the
limit. Now:
mpirun -hostfile myhostfile -np 14 ./a.out
causes the first 12 processes to be launched as before, but the remaining two
processes will be forced onto node cc. The other two nodes are protected by the
hostfile against oversubscription by this job.
Using the --nooversubscribe option can be helpful since Open MPI currently does not get
"max_slots" values from the resource manager.
Of course, -np can also be used with the -H or -host option. For example,
mpirun -H aa,bb -np 8 ./a.out
launches 8 processes. Since only two hosts are specified, after the first two
processes are mapped, one to aa and one to bb, the remaining processes oversubscribe
the specified hosts.
And here is a MIMD example:
mpirun -H aa -np 1 hostname : -H bb,cc -np 2 uptime
will launch process 0 running hostname on node aa and processes 1 and 2 each running
uptime on nodes bb and cc, respectively.
Process Binding
Processes may be bound to specific resources on a node. This can improve performance if
the operating system is placing processes suboptimally. For example, it might
oversubscribe some multi-core processor sockets, leaving other sockets idle; this can
lead processes to contend unnecessarily for common resources. Or, it might spread
processes out too widely; this can be suboptimal if application performance is sensitive
to interprocess communication costs. Binding can also keep the operating system from
migrating processes excessively, regardless of how optimally those processes were placed
to begin with.
To bind processes, one must first associate them with the resources on which they should
run. For example, the -bycore option associates the processes on a node with successive
cores. Or, -bysocket associates the processes with successive processor sockets, cycling
through the sockets in a round-robin fashion if necessary. And -cpus-per-proc indicates
how many cores to bind per process.
But, such association is meaningless unless the processes are actually bound to those
resources. The binding option specifies the granularity of binding -- say, with -bind-to-
core or -bind-to-socket. One can also turn binding off with -bind-to-none, which is
typically the default.
Finally, -report-bindings can be used to report bindings.
As an example, consider a node with two processor sockets, each comprising four cores. We
run mpirun with -np 4 -report-bindings and the following additional options:
% mpirun ... -bycore -bind-to-core
[...] ... binding child [...,0] to cpus 0001
[...] ... binding child [...,1] to cpus 0002
[...] ... binding child [...,2] to cpus 0004
[...] ... binding child [...,3] to cpus 0008
% mpirun ... -bysocket -bind-to-socket
[...] ... binding child [...,0] to socket 0 cpus 000f
[...] ... binding child [...,1] to socket 1 cpus 00f0
[...] ... binding child [...,2] to socket 0 cpus 000f
[...] ... binding child [...,3] to socket 1 cpus 00f0
% mpirun ... -cpus-per-proc 2 -bind-to-core
[...] ... binding child [...,0] to cpus 0003
[...] ... binding child [...,1] to cpus 000c
[...] ... binding child [...,2] to cpus 0030
[...] ... binding child [...,3] to cpus 00c0
% mpirun ... -bind-to-none
Here, -report-bindings shows the binding of each process as a mask. In the first case,
the processes bind to successive cores as indicated by the masks 0001, 0002, 0004, and
0008. In the second case, processes bind to all cores on successive sockets as indicated
by the masks 000f and 00f0. The processes cycle through the processor sockets in a round-
robin fashion as many times as are needed. In the third case, the masks show us that 2
cores have been bind per process. In the fourth case, binding is turned off and no
bindings are reported.
Open MPI's support for process binding depends on the underlying operating system.
Therefore, processing binding may not be available on every system.
Process binding can also be set with MCA parameters. Their usage is less convenient than
that of mpirun options. On the other hand, MCA parameters can be set not only on the
mpirun command line, but alternatively in a system or user mca-params.conf file or as
environment variables, as described in the MCA section below. The correspondences are:
mpirun option MCA parameter key value
-bycore rmaps_base_schedule_policy core
-bysocket rmaps_base_schedule_policy socket
-bind-to-core orte_process_binding core
-bind-to-socket orte_process_binding socket
-bind-to-none orte_process_binding none
The orte_process_binding value can also take on the :if-avail attribute. This attribute
means that processes will be bound only if this is supported on the underlying operating
system. Without the attribute, if there is no such support, the binding request results
in an error. For example, you could have
% cat $HOME/.openmpi/mca-params.conf
rmaps_base_schedule_policy = socket
orte_process_binding = socket:if-avail
Rankfiles
Rankfiles provide a means for specifying detailed information about how process ranks
should be mapped to nodes and how they should be bound. Consider the following:
cat myrankfile
rank 0=aa slot=1:0-2
rank 1=bb slot=0:0,1
rank 2=cc slot=1-2
mpirun -H aa,bb,cc,dd -rf myrankfile ./a.out
So that
Rank 0 runs on node aa, bound to socket 1, cores 0-2.
Rank 1 runs on node bb, bound to socket 0, cores 0 and 1.
Rank 2 runs on node cc, bound to cores 1 and 2.
Note that all slot locations are to be specified as physical indexes. You can use tools
such as HWLOC's "lstopo -v" to find the physical indexes of socket and cores.
Application Context or Executable Program?
To distinguish the two different forms, mpirun looks on the command line for --app option.
If it is specified, then the file named on the command line is assumed to be an
application context. If it is not specified, then the file is assumed to be an executable
program.
Locating Files
If no relative or absolute path is specified for a file, Open MPI will first look for
files by searching the directories specified by the --path option. If there is no --path
option set or if the file is not found at the --path location, then Open MPI will search
the user's PATH environment variable as defined on the source node(s).
If a relative directory is specified, it must be relative to the initial working directory
determined by the specific starter used. For example when using the rsh or ssh starters,
the initial directory is $HOME by default. Other starters may set the initial directory to
the current working directory from the invocation of mpirun.
Current Working Directory
The -wdir mpirun option (and its synonym, -wd) allows the user to change to an arbitrary
directory before the program is invoked. It can also be used in application context files
to specify working directories on specific nodes and/or for specific applications.
If the -wdir option appears both in a context file and on the command line, the context
file directory will override the command line value.
If the -wdir option is specified, Open MPI will attempt to change to the specified
directory on all of the remote nodes. If this fails, mpirun will abort.
If the -wdir option is not specified, Open MPI will send the directory name where mpirun
was invoked to each of the remote nodes. The remote nodes will try to change to that
directory. If they are unable (e.g., if the directory does not exist on that node), then
Open MPI will use the default directory determined by the starter.
All directory changing occurs before the user's program is invoked; it does not wait until
MPI_INIT is called.
Standard I/O
Open MPI directs UNIX standard input to /dev/null on all processes except the
MPI_COMM_WORLD rank 0 process. The MPI_COMM_WORLD rank 0 process inherits standard input
from mpirun. Note: The node that invoked mpirun need not be the same as the node where
the MPI_COMM_WORLD rank 0 process resides. Open MPI handles the redirection of mpirun's
standard input to the rank 0 process.
Open MPI directs UNIX standard output and error from remote nodes to the node that invoked
mpirun and prints it on the standard output/error of mpirun. Local processes inherit the
standard output/error of mpirun and transfer to it directly.
Thus it is possible to redirect standard I/O for Open MPI applications by using the
typical shell redirection procedure on mpirun.
% mpirun -np 2 my_app < my_input > my_output
Note that in this example only the MPI_COMM_WORLD rank 0 process will receive the stream
from my_input on stdin. The stdin on all the other nodes will be tied to /dev/null.
However, the stdout from all nodes will be collected into the my_output file.
Signal Propagation
When orterun receives a SIGTERM and SIGINT, it will attempt to kill the entire job by
sending all processes in the job a SIGTERM, waiting a small number of seconds, then
sending all processes in the job a SIGKILL.
SIGUSR1 and SIGUSR2 signals received by orterun are propagated to all processes in the
job.
One can turn on forwarding of SIGSTOP and SIGCONT to the program executed by mpirun by
setting the MCA parameter orte_forward_job_control to 1. A SIGTSTOP signal to mpirun will
then cause a SIGSTOP signal to be sent to all of the programs started by mpirun and
likewise a SIGCONT signal to mpirun will cause a SIGCONT sent.
Other signals are not currently propagated by orterun.
Process Termination / Signal Handling
During the run of an MPI application, if any rank dies abnormally (either exiting before
invoking MPI_FINALIZE, or dying as the result of a signal), mpirun will print out an error
message and kill the rest of the MPI application.
User signal handlers should probably avoid trying to cleanup MPI state (Open MPI is
currently not async-signal-safe; see MPI_Init_thread(3) for details about
MPI_THREAD_MULTIPLE and thread safety). For example, if a segmentation fault occurs in
MPI_SEND (perhaps because a bad buffer was passed in) and a user signal handler is
invoked, if this user handler attempts to invoke MPI_FINALIZE, Bad Things could happen
since Open MPI was already "in" MPI when the error occurred. Since mpirun will notice
that the process died due to a signal, it is probably not necessary (and safest) for the
user to only clean up non-MPI state.
Process Environment
Processes in the MPI application inherit their environment from the Open RTE daemon upon
the node on which they are running. The environment is typically inherited from the
user's shell. On remote nodes, the exact environment is determined by the boot MCA module
used. The rsh launch module, for example, uses either rsh/ssh to launch the Open RTE
daemon on remote nodes, and typically executes one or more of the user's shell-setup files
before launching the Open RTE daemon. When running dynamically linked applications which
require the LD_LIBRARY_PATH environment variable to be set, care must be taken to ensure
that it is correctly set when booting Open MPI.
See the "Remote Execution" section for more details.
Remote Execution
Open MPI requires that the PATH environment variable be set to find executables on remote
nodes (this is typically only necessary in rsh- or ssh-based environments --
batch/scheduled environments typically copy the current environment to the execution of
remote jobs, so if the current environment has PATH and/or LD_LIBRARY_PATH set properly,
the remote nodes will also have it set properly). If Open MPI was compiled with shared
library support, it may also be necessary to have the LD_LIBRARY_PATH environment variable
set on remote nodes as well (especially to find the shared libraries required to run user
MPI applications).
However, it is not always desirable or possible to edit shell startup files to set PATH
and/or LD_LIBRARY_PATH. The --prefix option is provided for some simple configurations
where this is not possible.
The --prefix option takes a single argument: the base directory on the remote node where
Open MPI is installed. Open MPI will use this directory to set the remote PATH and
LD_LIBRARY_PATH before executing any Open MPI or user applications. This allows running
Open MPI jobs without having pre-configured the PATH and LD_LIBRARY_PATH on the remote
nodes.
Open MPI adds the basename of the current node's "bindir" (the directory where Open MPI's
executables are installed) to the prefix and uses that to set the PATH on the remote node.
Similarly, Open MPI adds the basename of the current node's "libdir" (the directory where
Open MPI's libraries are installed) to the prefix and uses that to set the LD_LIBRARY_PATH
on the remote node. For example:
Local bindir: /local/node/directory/bin
Local libdir: /local/node/directory/lib64
If the following command line is used:
% mpirun --prefix /remote/node/directory
Open MPI will add "/remote/node/directory/bin" to the PATH and
"/remote/node/directory/lib64" to the D_LIBRARY_PATH on the remote node before attempting
to execute anything.
The --prefix option is not sufficient if the installation paths on the remote node are
different than the local node (e.g., if "/lib" is used on the local node, but "/lib64" is
used on the remote node), or if the installation paths are something other than a
subdirectory under a common prefix.
Note that executing mpirun via an absolute pathname is equivalent to specifying --prefix
without the last subdirectory in the absolute pathname to mpirun. For example:
% /usr/local/bin/mpirun ...
is equivalent to
% mpirun --prefix /usr/local
Exported Environment Variables
All environment variables that are named in the form OMPI_* will automatically be exported
to new processes on the local and remote nodes. The -x option to mpirun can be used to
export specific environment variables to the new processes. While the syntax of the -x
option allows the definition of new variables, note that the parser for this option is
currently not very sophisticated - it does not even understand quoted values. Users are
advised to set variables in the environment and use -x to export them; not to define them.
Setting MCA Parameters
The -mca switch allows the passing of parameters to various MCA (Modular Component
Architecture) modules. MCA modules have direct impact on MPI programs because they allow
tunable parameters to be set at run time (such as which BTL communication device driver to
use, what parameters to pass to that BTL, etc.).
The -mca switch takes two arguments: <key> and <value>. The <key> argument generally
specifies which MCA module will receive the value. For example, the <key> "btl" is used
to select which BTL to be used for transporting MPI messages. The <value> argument is the
value that is passed. For example:
mpirun -mca btl tcp,self -np 1 foo
Tells Open MPI to use the "tcp" and "self" BTLs, and to run a single copy of "foo" an
allocated node.
mpirun -mca btl self -np 1 foo
Tells Open MPI to use the "self" BTL, and to run a single copy of "foo" an allocated
node.
The -mca switch can be used multiple times to specify different <key> and/or <value>
arguments. If the same <key> is specified more than once, the <value>s are concatenated
with a comma (",") separating them.
Note that the -mca switch is simply a shortcut for setting environment variables. The
same effect may be accomplished by setting corresponding environment variables before
running mpirun. The form of the environment variables that Open MPI sets is:
OMPI_MCA_<key>=<value>
Thus, the -mca switch overrides any previously set environment variables. The -mca
settings similarly override MCA parameters set in the $OPAL_PREFIX/etc/openmpi-mca-
params.conf or $HOME/.openmpi/mca-params.conf file.
Unknown <key> arguments are still set as environment variable -- they are not checked (by
mpirun) for correctness. Illegal or incorrect <value> arguments may or may not be
reported -- it depends on the specific MCA module.
To find the available component types under the MCA architecture, or to find the available
parameters for a specific component, use the ompi_info command. See the ompi_info(1) man
page for detailed information on the command.
Exit status
There is no standard definition for what mpirun should return as an exit status. After
considerable discussion, we settled on the following method for assigning the mpirun exit
status (note: in the following description, the "primary" job is the initial application
started by mpirun - all jobs that are spawned by that job are designated "secondary"
jobs):
· if all processes in the primary job normally terminate with exit status 0, we return 0
· if one or more processes in the primary job normally terminate with non-zero exit
status, we return the exit status of the lowest rank to have a non-zero status
· if all processes in the primary job normally terminate with exit status 0, and one or
more processes in a secondary job normally terminate with non-zero exit status, we (a)
return the exit status of the lowest rank in the lowest jobid to have a non-zero status,
and (b) output a message summarizing the exit status of the primary and all secondary
jobs.
· if the cmd line option --report-child-jobs-separately is set, we will return -only- the
exit status of the primary job. Any non-zero exit status in secondary jobs will be
reported solely in a summary print statement.
By default, OMPI records and notes that MPI processes exited with non-zero termination
status. This is generally not considered an "abnormal termination" - i.e., OMPI will not
abort an MPI job if one or more processes return a non-zero status. Instead, the default
behavior simply reports the number of processes terminating with non-zero status upon
completion of the job.
However, in some cases it can be desirable to have the job abort when any process
terminates with non-zero status. For example, a non-MPI job might detect a bad result from
a calculation and want to abort, but doesn't want to generate a core file. Or an MPI job
might continue past a call to MPI_Finalize, but indicate that all processes should abort
due to some post-MPI result.
It is not anticipated that this situation will occur frequently. However, in the interest
of serving the broader community, OMPI now has a means for allowing users to direct that
jobs be aborted upon any process exiting with non-zero status. Setting the MCA parameter
"orte_abort_on_non_zero_status" to 1 will cause OMPI to abort all processes once any
process
exits with non-zero status.
Terminations caused in this manner will be reported on the console as an "abnormal
termination", with the first process to so exit identified along with its exit status.
EXAMPLES
Be sure also to see the examples throughout the sections above.
mpirun -np 4 -mca btl ib,tcp,self prog1
Run 4 copies of prog1 using the "ib", "tcp", and "self" BTL's for the transport of MPI
messages.
mpirun -np 4 -mca btl tcp,sm,self
--mca btl_tcp_if_include eth0 prog1
Run 4 copies of prog1 using the "tcp", "sm" and "self" BTLs for the transport of MPI
messages, with TCP using only the eth0 interface to communicate. Note that other BTLs
have similar if_include MCA parameters.
RETURN VALUE
mpirun returns 0 if all ranks started by mpirun exit after calling MPI_FINALIZE. A non-
zero value is returned if an internal error occurred in mpirun, or one or more ranks
exited before calling MPI_FINALIZE. If an internal error occurred in mpirun, the
corresponding error code is returned. In the event that one or more ranks exit before
calling MPI_FINALIZE, the return value of the rank of the process that mpirun first
notices died before calling MPI_FINALIZE will be returned. Note that, in general, this
will be the first rank that died but is not guaranteed to be so.
SEE ALSO
MPI_Init_thread(3)